*see explainations to the ping pong ball demo at the bottom
Summary of Today's Lesson
Collision Theory States: particles must collide to react, however, for a successful collision to occur, the particles must meet the following reqirements:
a) minimum kinetic energy
b) correct orientation
The distribution of kinetic energy of particles can be represented in the following graph: (this is much like the student vs. height example in class, except that it is dealing wtih particles which also shifts the graph to the left compared to the Graussian model)
This particular shape of distribution is named the Maxwell-Boltzman Distribution:
Activation Energy is the minimum amount of energy required for a reaction to occur.
In the following graph, an exothermic reaction is taking place where the activation energy is the energy required to move the reactants to the transition state (represented by the top-most dotted red line) and enthalpy change is the heat evolved during this reaction.
For more detailed information on collision and KM theory, visit: http://www.chemguide.co.uk/physical/basicrates/introduction.html http://www.emsb.qc.ca/laurenhill/science/kinetic.html
Through the ping pong ball activity, I illustrated aspects of the collision theory.
The ping pong ball thesmselves represent particles with specific orientations (in this case there are two orientations for each particle represented by different colors)
To achieve a bond, the following are needed:
1. Correct amount of force in throw which is translated into sufficient energy exerted by the movement of the particles.
2. Matching the same colors which result in the particles bonding when they collide with the correct orientations.
*note: in the demo, the ping pong balls bounces off of each other despite of their colliding orientation. In reality, particles colliding with sufficient energy and correct orientation bond instead of bouncing off.
Since the particles are constantly moving, the volume they take up isn't the particle themselves, but the space they are allowed to occupy, in other words, it is defined by the shape of the container that holds them. In the demo, the volume the particles take up is defined by the classroom, or the people throwing them if they had never dropped the balls.
In order for molecules to decompose, they need to:
1. Hit themselves against the container wall to convert kinetic to potential energy (in this case, potential energy is reperesented by the potential force from people throwing these ping pong balls)
2. Colliding with other particles (again, particles also need to collide with a specific orientation to break a bond)
3. Use light energy to break bonds
The rate of a given reaction can be represented by this equation:
Rate = frequency of collisions x fraction of collisoins that are effective
Through throwing the ping pong balls, you may have noticed that having 3 of the same colors collide is more difficult than having two collide.
In reality, the probabiliy of three-particle collisions are very small. This is because the chance of having three particles at the exact time, place and orientation is not very likely. And four-particle collisions are even more unlikely. (keep in mind that during the demo in class, we throw the balls intentionally in a certain direction for them to hit, in reality, particles don't think like we do)
Since multiple particle collisions are not very probable, most chemical reactions occur in elementary steps that make up an overall reaction
Just some definitions.. Elementary step: a step in a reaction mechanism that only involves one-,two-, or three-particle collisions Reaction mechanism: a series of elementary steps that make up an overall reaction.
Collision and KM Theory
*see explainations to the ping pong ball demo at the bottom
Summary of Today's Lesson
Collision Theory States: particles must collide to react, however, for a successful collision to occur, the particles must meet the following reqirements:a) minimum kinetic energy
b) correct orientation
The distribution of kinetic energy of particles can be represented in the following graph: (this is much like the student vs. height example in class, except that it is dealing wtih particles which also shifts the graph to the left compared to the Graussian model)
This particular shape of distribution is named the Maxwell-Boltzman Distribution:
Activation Energy is the minimum amount of energy required for a reaction to occur.
In the following graph, an exothermic reaction is taking place where the activation energy is the energy required to move the reactants to the transition state (represented by the top-most dotted red line) and enthalpy change is the heat evolved during this reaction.
For more detailed information on collision and KM theory, visit: http://www.chemguide.co.uk/physical/basicrates/introduction.html
http://www.emsb.qc.ca/laurenhill/science/kinetic.html
The above graphs are taken from: http://www.chemguide.co.uk/physical/basicrates/introduction.html
Ping Pong Ball Activity:
The ping pong ball thesmselves represent particles with specific orientations (in this case there are two orientations for each particle represented by different colors)
To achieve a bond, the following are needed:
1. Correct amount of force in throw which is translated into sufficient energy exerted by the movement of the particles.
2. Matching the same colors which result in the particles bonding when they collide with the correct orientations.
*note: in the demo, the ping pong balls bounces off of each other despite of their colliding orientation. In reality, particles colliding with sufficient energy and correct orientation bond instead of bouncing off.
Since the particles are constantly moving, the volume they take up isn't the particle themselves, but the space they are allowed to occupy, in other words, it is defined by the shape of the container that holds them. In the demo, the volume the particles take up is defined by the classroom, or the people throwing them if they had never dropped the balls.
In order for molecules to decompose, they need to:
1. Hit themselves against the container wall to convert kinetic to potential energy (in this case, potential energy is reperesented by the potential force from people throwing these ping pong balls)
2. Colliding with other particles (again, particles also need to collide with a specific orientation to break a bond)
3. Use light energy to break bonds
The rate of a given reaction can be represented by this equation:
Rate = frequency of collisions x fraction of collisoins that are effective
Through throwing the ping pong balls, you may have noticed that having 3 of the same colors collide is more difficult than having two collide.
In reality, the probabiliy of three-particle collisions are very small. This is because the chance of having three particles at the exact time, place and orientation is not very likely. And four-particle collisions are even more unlikely. (keep in mind that during the demo in class, we throw the balls intentionally in a certain direction for them to hit, in reality, particles don't think like we do)
Since multiple particle collisions are not very probable, most chemical reactions occur in elementary steps that make up an overall reaction
Just some definitions..
Elementary step: a step in a reaction mechanism that only involves one-,two-, or three-particle collisions
Reaction mechanism: a series of elementary steps that make up an overall reaction.